1. Field of the Invention
The present invention relates to a method for manufacturing an electro-optical device including a flexographic process. More particularly, the present invention relates to a flexographic technique in the manufacturing method.
2. Description of the Related Art
In electronic devices, such as mobile telephones, displays are formed of electro-optical devices. The most typical electro-optical device is a liquid crystal device that uses liquid crystal as the electro-optical substance.
As shown in FIGS. 2 and 3(A), in a liquid crystal device 400, a liquid crystal 404 serving as an electro-optical substance is held between a first transparent substrate 410 and a second transparent substrate 420 which are placed so that electrode patterns 440 and 450 formed on the surfaces thereof are opposed to each other.
In order to construct such a liquid crystal device 400, after red (R), green (G), and blue (B) color filters 407R, 407G, and 407B are formed on the second transparent substrate 420, a planarizing film 427, the second electrode patterns 450, an insulating overcoating film 429, and an alignment film 416 made of polyimide resin are formed in that order on the front sides of the color filters 407R, 407G, and 407B. The first electrode patterns 440 and an alignment film 412 made of polyimide resin are formed in that order on the first transparent substrate 410.
In the first transparent substrate 410 and the second transparent substrate 420, as shown in FIG. 2, a first terminal region 411 and a second terminal region 421 are formed along substrate edges 418 and 428. Conductive connection between the substrates and connection with a flexible substrate 70 are performed in these terminal regions. Therefore, the alignment films 412 and 416 and the overcoating film 429 are not formed in the first terminal region 411 and the second terminal region 421 on the first transparent substrate 410 and the second transparent substrate 420.
For this reason, the sides of the surfaces of the first transparent substrate 410 and the second transparent substrate 420 in the lengthwise direction (the direction shown by arrow L in FIG. 2), on which the first terminal region 411 and the second terminal region 421 are formed, serve as uncoated areas 12 which need not be coated with films, such as the alignment films 412 and 416 and the overcoating film 429. The sides on which a liquid-crystal-sealed region 435 is formed serve as coated areas 11 which need to be coated with films, such as the alignment films 412 and 416 and the overcoating film 429. Therefore, it is necessary to selectively form the alignment films 412 and 416 and the overcoating film 429 on the surfaces of the first transparent substrate 410 and the second transparent substrate 420.
Accordingly, the alignment films 412 and 416, the overcoating film 429, and are formed by flexography. In a coating device 100 used in flexography, as shown in FIG. 5, coating liquid is transferred from an anilox roller 130 onto a letterpress 110 which is mounted around a drum 120, and the coating liquid transferred onto projections 111 formed on the surface of the letterpress 110 is transferred onto a substrate.
As shown in FIGS. 6(A) and 6(B), meshes 139 are formed at a pitch P2 on the surface of the anilox roller 130 in order to enhance the coating liquid holding ability. As shown in FIGS. 7(A) and 7(B), meshes 119 are also formed at a pitch P3 on the surfaces of the projections 111 of the letterpress 110 in order to enhance the coating liquid holding ability.
Problems to be Solved by the Invention
Since the color filters 407R, 407G, and 407B are formed in a predetermined repetitive pattern on the surface of the second transparent substrate 420 which is subjected to such flexography, as shown in FIG. 3(B), color filters of the same color, of the color filters 407R, 407G, and 407B, are formed at a predetermined pitch P1 (same-color pitch).
In the coating device 100 which has been described with reference to FIGS. 5, 6, and 7, when a film for forming the alignment film 416 is transferred from the letterpress 110 onto the second transparent substrate 420, marks of the meshes 139 of the anilox roller 130 and marks of the meshes 119 formed on the surfaces of the projections 111 of the letterpress 110 are made on the surface of the transferred film.
Therefore, in the second transparent substrate 420, the marks of the meshes 139 of the anilox roller 130 and the marks of the meshes 119 formed on the surfaces of the projections 111 of the letterpress 110 are transferred onto the alignment film 416, and the color filters of the same color, of the color filters 407R, 407G, and 407B, are formed at a predetermined same-color pitch P1 on a layer disposed thereunder. Moreover, the pitch P2 of the meshes 139 of the anilox roller 130, the pitch P3 of the meshes 119 formed on the surfaces of the projections 111 of the letterpress 110, and the pitch P1 of the color filters of the same color, of the color filters 407R, 407G, and 407B, are substantially equal, but are slightly different from one another.
For this reason, in the second transparent substrate 420, the color filters 407R, 407G, and 407B with the same-color pitch P1, the marks of the meshes 139 of the anilox roller 130, and the marks of the meshes 119 on the projections 111 of the letter press 110 interfere with one another and cause moire. This decreases the quality of images formed by the liquid crystal device 410.
In view of the above problems, it is a feature of the present invention to provide a method for manufacturing an electro-optical device in which moiré can be prevented even when films are formed on the front sides of color filters by flexography.